Link connector and control equipment for routine and priority connections to operator positions



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LINK CONNECTOR AND CONTROL EQUIPMENT FOR ROUTINE AND PRIORITY CONNECTIONS TO OPERATOR POSITIONS Original Filed Oct. 25, 1963 13 Sheets-Sheet 15 United States Patent C LINK CONNECTOR AND CONTROL EQUIPMENT FOR ROUTINE AND PRIORITY CONNECTIONS TO OPERATOR POSITIONS Arnold H. Scheinman, Silver Spring, Md., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Continuation of application Ser. No. 318,360, Oct. 23, 1963. This application Nov. 4, 1966, Ser. No. 592,235

20 Claims. (Cl. 179-27) ABSTRACT OF THE DISCLOSURE A tandem telephone system is disclosed employing common control facilities including markers, senders and data transfer circuits for controlling crossbar networks to switch a variety of special service calls from origina'iing to terminating otfices via special service and dial trunk circuits. The system utilizes operator assistance for serving such calls. It is provided with position link connector and controller equipment for successively connecting the calls from the trunk circuits to operator positions on priority and non-priority bases during periods of each call when operator assistance is desired.

This is a continuation of application Ser. No. 318,360 filed Oct. 23, 1963, now abandoned and relates to switching systems and particularly to switching equipment for connecting telephone calls to operator positions for service. The present invention further relates to equipment which enables calling circuits to be selectively connected to operator positions on non-priority and priority bases. This invention more particularly relates to equipment which minimizes the holding time of operator position facilities on calls requiring assistance for their completion and which provides for prompt, efiicient operator service. The equipment accomplishes these advantageous results by initially connecting a call to an operator position on a non-priority basis, by disconnecting it from the position during periods of the call when operator assistance i not required, and by selectively reconneciing it to the same or another operator position on a priority basis when assistance again is needed on the call.

A substantial percentage of the calls served by present day telephone systems are completed with 'the assistance of operators. Included among the types of calls currently requiring operator assistance are those classified as: dial 0, person-to-person, credit card, collect, and charge-toa-third-party, as well as certain coin calls. These calls are often referred to as special service calls because the calling party requires some sort of special service from an operator for establishing connections to the called station, as well as further operator assistance at periodic intervals during the remainder of the call.

In recent years, considerable etfort has been expended in developing new and advanced techniques, methods and automatic facilities for minimizing the amount of operator assistance provided for special service calls. While such developments have succeeded to a great extent in reducing many of the laborious tasks performed by an operator during a special service call, they have not entirely eliminated the need for furnishing prompt and eliicient operator assistance to the calling party at any time after the calling and called stations have been interconnected and the call is in progress.

To provide prompt operator assistance to the customer while a special service call is in progress, it has heretofore been necessary for a communication channel to remain established between the operator position facilities and the calling circuit for the entire duration of the call so that the operator may be signaled at any time to provide the desired assistance. While the need for maintaining such a channel yet persists in existing telephone systems, the channel is unfortunately being used inefiiciently because recent advances in the art have now made communication between the calling party and the operator necessary only during a few short periods on each call.

In addition, it has been customary in the past to furnish a large number of such communication channels to each operator position for enabling the operator to serve many different special service calls on an overlapping basis. Such an arrangement has been necessary in order to minimize the time periods during which the operator is not serving calls. Even though the utilization of such channels has provided for the efiicient use of operator time and for the best quality service to telephone cus tomers on special service calls, the cost of such channels has proven an economic burden on the telephone companies and, as well, has contributed greatly to the customer cost for such calls.

It may be appreciated from the foregoing that a need exists for a less costly and more efiicient means of providing for prompt operator assistance on special service calls, and par'icularly during those periods while such calls are in progress.

Accordingly, it is a general object of my invention to provide a more efficient and less costly means for furnishing prompt operator assistance on special service calls.

It is another object of this invention to provide switching equipment which minimizes the holding time of operator position facilities on special service calls.

Another object of the'present invention is to provide switching equipment for efficiently utilizing communication channels between calling circuits and operator, position facilities on special service calls.

These and other objects are attained in accordance with an exemplary embodiment of my invention wherein switching equipment is provided for initially connecting an incoming special service call over a communication channel to an operator position for service, for subsequently releasing that channel to disconnect the call from the position during those periods when operator assistance is not required, and for thereafter connecting the call over the same or another channel to the same or another operator position when assistance again is needed. In accordance with the exemplary embodiment, each special service call is received by an incoming trunk circuit and is connected to an operator position over a communication channel comprising a path through a position link connector.

Each of the trunk circuits is equipped with a pair of start leads to a position link connector. One of these leads is used by the trunk circuit for presenting the request to a position link connector that connections be established on a' non-priority service basis through that position link to an available operator position. Such service may be requested by a trunk circuit when it initially receives a special service call. This type of service is requested at such periods because operator assistance is not required as quickly at that time as it is while the call is in progress. After the connections have been established from the calling trunk circuit to an operator position and the operator has furnished the needed assistance, the operator may transfer supervision over the special service call to the calling trunk circuit and then effect the release of the connections between that trunk circuit and her position in order that it may be again available to serve other calls.

The second start lead is used by the trunk circuit to present a request to the position link connector for connections to an operator position on a priority service basis. Such service may be requested by the trunk circuit, for example, while a special service call is in progress in order that prompt and eflicient operator service may be furnished to the customer with minimum delay.

A position link connector provides for the termination of a plurality of different groups of incoming trunk circuits. Each of these trunk groups may serve a different c'lass-of-call. For example, one such group may serve the dial calls, a second group may serve person-to-person calls, and another group may serve the coin calls. A position link connector together with a position link controller provides the means for interconnecting the trunk circuits with the position circuits. The position link provides the actual interconnecting means and the link controller controls the operation of a plurality of such position links to establish the interconnections.

Each position link comprises individual non-priority and priority registers for each trunk group to register their request for service. Non-priority request signals are received by the position link over the non-priority start leads and are applied to the appropriate non-priority registers through individual class-of-service gate circuits. The latter circuits cooperate with a traffic regulator circuit to interconnect the trunk circuits to available operator positions in the approximate order in which their non-priority requests are presented.

The trafiic regulator enables the non-priority request signals from a plurality of trunk circuits, for example trunk circuits in a dial 0 trunk group, to be extended through the class-of-service gates and be registered at the same time. Immediately thereafter, it activates these gates to block the registration of non-priority requests from other trunk circuits in all dial 0 trunk groups served by the regulator. While the latter circuits are being blocked from having their non-priority request registered, the regulator enables the gates associated with the trunk circuits serving other classes-of-calls, for example coin calls, to have their non-priority requests registered in their nonpriority registers. These latter coin trunk circuits may then compete with the dial 0 trunk circuits for connections to operator positions.

For obtaining connections to an operator position on a priority service basis, the priority start leads associated with the incoming trunk circuits are connected directly to the priority registers of the position links independently of any gating system. This arrangement enables the trunk circuits to register immediately their priority request and, as a result, to' effect the operation of the position link in such a fashion as to enable these circuits to be connected to available operator positions before the non-priority requesting trunk circuits in the same trunk group. After a priority request has been registered for a trunk group, for example a dial 0 group, the gates associated with the non-priority registers are opened to block the registration of non-priority requests until after all the priority requesting trunk circuits in that group have been served.

In the present exemplary embodiment, a plurality of position links are controlled .by a fewer number of position link controllers in order to realize equipment economy while at the same time providing for the speedy establishment of interconnections between calling trunk circuits and operator positions. Also, facilities are included in this embodiment for selectively preconditioning the operator positions to serve some or all of the different classes-ofcalls. a

, When non-priority and/or priority requests have been registered as explained, the associated position links bid seizes an idle controller in order that connections may be established from the calling trunk circuits to operator positions.

If a priority request has been registered, the position link having such a request is given preference over those position links having registered non-priority requests, in their bids for seizing an idle controller. The order of preference is controlled by the traflic regulator. When a trunk circuit requests priority service, the regulator is activated to make all operator positions appear busy to all position links except those having registered priority requests. In this manner, only the position links having priority requests are enabled to seize an idle link controller. Consequently, the priority requesting trunk circuits will be connected with idle positions before those requesting nonpriority service.

After a position link controller has been seized, the link connector informs it of the trunk groups which have calling trunk circuits currently requesting non-priority and priority service. The link controller then selects the most preferred one of the trunk groups and the trunk circuit within the preferred group which will be served. In this selection operation, the controller will prefer those trunk groups which have trunk circuits requesting priority service over those groups which have trunk groups requesting only non-priority service.

Thereafter, the controller informs the position link of the identity of the preferred trunk group and then receives back from that connector a class-of-service indication which indicates the type of service required by the call on the preferred trunk circuit. The latter indication allows the controller to initiate the selection of a position capable of serving the call. 7

Following the selection of an operator position, the controller establishes connections from the preferred trunk circuit through a switching network in the position link to the selected position. At approximately the same time, other common control circuits are activated for lighting lamps at the operator position to inform the operator of the service needed on the call. When this service has been furnished, the operator may effect the release of the connections extending from her position through the position link to the calling trunk circuit and transfer supervision over the call to the latter circuit. Upon the completion of the latter operation, the operator is then free to serve another call.

A feature of this invention is the provision of a connector for initially connecting a callfrom a communication lineto an operator position on a routine basis for service, facilities for controlling the connector to disconnect that position from the line during the call, and means which may be thereafter operated by a signal received from the line during the call for activating the connector to reconnect that line to the position on a priority basis.

Another feature of the present invention is the provision of a connector which is responsive to the receipt of a call on a communication line circuit for initially connecting that circuit to any one of a plurality of operator positions for service, means for controlling the connector to disconnect the circuit from the position after the service has been furnished, and means thereafter responsive to a signal received from the circuit during the call for activating the connector to connect the circuit selectively to any one of said positions when operator assistance again is needed.

A further feature of my invention is the provision of a group of trunks each of which is entitled to connections to a plurality of operator positions on both routine and priority bases, a registration circuit for registering routine requests received from any of the trunks, a selection circuit which is controlled by the registration circuit and is responsive to a priority connection request from any one of the trunks for selecting the priority requesting trunk for connection to any one of the operator positions before any of the trunks having a registered routine request,

and a connector activated by the selection circuit for connecting each selected trunk to one of said positions.

Yet another feature of this invention is the provision of a plurality of trunk circuits each of which has a first conductor used for requesting connections to operator positions on a routine basis and a second conductor used for requesting connections to the operator positions on a priority basis and interconnecting means which is responsive to the receipt of routine and priority connection requests from said conductors for interconnecting each of the priority requesting circuits with a position before interconnecting the routine connection requesting circuits with the positions.

Still another feature is the provision of a connector which is activated by a plurality of trunk circuits upon the receipt of calls therein, for successively establishing an initial connection from each of the calling circuits and an operator position, facilities at each operator position for effecting the release of the initial connection between that position and a calling circuit during periods when operator assistance is not required, and means thereafter responsive to a signal received from a disconnected circuit for op rating the connector to connect the latter circuit to an operator position before any of the circuits awaiting the establishment of an initial connection to an operator position.

Another feature is the provision of equipment for a switching system, which equipment includes trunk circuits each havin a first conductor used for requesting routine connections to any of a plurality of operator positions, a second conductor used for requesting priority connections to any of the operator positions and means responsive to the receipt of a call for applying a request signal to the first conductor, an interconnecting network which is responsive to the receipt of the request signals from the first conductors for interconnecting each of the requesting trunk circuits with an individual one of the operator positions in a routine succession, facilities for releasing the established interconnections between any of the trunk circuits and an operator position during periods of a call when operator assistance is not required, and additional means in each of the released trunk circuits for thereafter selectively applying a priority request signal to its second conductor when operator assistance again is required, for activating the interconnecting network to interconnect that circuit with one of the positions before any one of the trunk circuits requesting routine connections.

Another feature is the provision of equipment for a switching system, which equipment comprises trunk circuits each having a first signaling means used for requesting connections to any of a plurality of operator positions on a routine basis, and a second signaling means used for requesting connections to any of the operator positions on a priority basis, a position connector comprising switch means for connecting any one of said circuits to any of said positions and a pair of registers each being individually associated with one of the signaling means of each of the trunk circuits for registering the routine and priority connection requests received from these circuits, and means responsive to the registration of routine and priority connection requests in said registers for activating said switch means to connect each of the trunk circuits having registered priority requests to an operator position before any of the circuits having a registered routine request.

A further feature is the provision of equipment for a telephone system, which equipment comprises groups of trunk circuits, each of the groups being used for serving a different class-of-call such as dial 0 or person-toperson or coin calls, a plurality of operator positions each being selectively preconditioned for serving predetermined ones of said classes-of-calls, a plurality of position connectors each being individually associated with a predetermined number of the trunk groups and each comprising switch means operable for interconnecting said associated circuits with any of the operator positions, means activated by any one of said associated trunk circuits upon the receipt of a call therein for registering a request by that trunk circuit for connection to one of the operator positions, means for indicating the availability of said positions to serve the call in the requesting trunk circuit and means controlled by the indicating means and responsive to the activation of the registering means for supplying a start signal to a common control circuit when one of the positions is available to serve the call, the control circuit then being effective to operate the switch means to interconnect each of the circuits having a register request with one of the available positions.

Another feature is the provision of equipment for a telephone system which equipment includes groups of trunk circuits, each of the groups being used for serving a different class-of-call, a plurality of operator positions being selectively preconditioned for serving predeter mined ones or" said classes-of-calls, each of the trunk circuits having a first conductor used for requesting connections to the operator positions on a non-priority basis and a second conductor used for requesting connections to the positions on a priority basis, and a plurality of position link connectors each of which is individually associated with a predetermined number of the groups of trunk circuits and each of which comprises a switching network operable for interconnecting any one of the associated trunk circuits with any one of the operator positions, a pair of registers each individually associated with one of the conductors of each of the associated trunk circuits for registering the non-priority and priority connection requests, means responsive to the registration of requests in the registers for identifying the classes-ofcalls served by the requesting circuits, means for indicating the availability of the operator positions to serve the calls in the requesting circuits, means controlled by the indicating means and responsive to the registration of a connection request in one of the registers for supplying a start signal to one of a plurality of position link controllers for initiating a sequence of circuit actions which result in the operation of the switching network to interconnect the connection requesting trunk circuits to available operator positions in a predetermined order.

Another feature directly related to the immediately preceding one is the provision of a number of position link controllers for serving a greater number of position link connectors. Each of these controllers comprises means activated by a start signal from any one of the position link connectors for storing the identity of each of the groups of trunk circuits having a registered request, means activated by the storing means for selecting priority requesting trunk circuit and then non-priority requesting trunk circuit in each of the latter trunk groups for connection to an individual operator position, means operated by the selecting means for receiving the identity of the class-of-call served by each selected circuit from the identifying means of the associated position link connector, means operated by the receiving means for selecting one of the operator positions available to serve the call in the selected circuit, and means activated by the position selecting means for activating the switch means of the position link connector to interconnect the selected trunk circuit with the selected position.

It is another feature of my invention that a position link controller serve the priority requesting trunk circuits and then the non-priority requesting trunk circuits in a trunk group and thereafter advance to another trunk group having priority and/or non-priority requesting trunk circuits.

An advantage of my invention over the prior art is that a communication channel between a calling trunk circuit and an operator position is efficiently used because it is not maintained during those periods of a special service call when operator assistance is not needed.

This also enables the operator position facilities to be free to serve other calls instead of being tied up for the duration of a special service call as in prior art arrangements. Another advantage is that a trunk circuit may selectively request connections to operator positions on both routine and priority bases. The provision of the facilities whereby a trunk circuit may obtain priority connections to an operator position over other trunk circuits is a salient advantage of the present invention for, as in the exemplary embodiment, it enables the trunk circuit to be connected to an operator position with minimum delay during the periods of a call when the calling party is being charged for the call.

The foregoing objects, features, and advantages, as well as others, of this invention may become more apparent from a reading of the following description with reference to the drawing in which:

FIG. 1 shows, in block diagram form, the equipment of a tandem telephone system in which the equipment illustrative of the principles of the present invention has been embodied;

FIG. 2 is a block diagram depicting the equipment of the illustrative embodiment and comprises a group of ten position link connectors employed in the tandem system for connecting 500 incoming trunk circuits to 66 operator positions through position control circuits and position circuits under the control of three position link controllers, a traffic regulator, and a key control position control circuit;

FIGS. 3-13, inclusive, show in block and schematic form the essential circuit details of an incoming dial 6 trunk circuit, a special service trunk circuit, a position link connector, a position link controller and a traffic regulator comprising the equipment utilized for connecting incoming calls to operators on both non-priority and priority bases; and

FIG. 14 depicts the position in which FIGS. 1, 2 and 3-13 should be placed to show the cooperation between the equipment units. a

t is noted that FIGS. 3-13 employ a type of schematic notation referred to as detached-contact in which an X crossing a line represents a normally opened contact of a relay and a bar crossing a line represents a normally closed contact of a relay; normally referring to the unoperated condition of a relay. The principles of this type of notation are described in an article entitled An improved Dctached-Contact-Type Schematic Circuit Drawing by F. T. Meyer in the September 1955 publication of the American Institute of Electrical Engineers (AiEE) Transactions, Communications and Electronics, vol. 74, pages Q5-5l3.

Each relay contact is designated in the drawing in a manner which indicates the relay of which it is a part and'as well uniquely identifies it with respect to other contacts of the relay. For example, referring to relay contact Mfi-1 on FIG. 3, it is noted that the M69 position of the designation indicates that it is controlled by relay Mild of FIG. 3 and the i uniquely identifies it with respect to the other contact M994 of relay Mud, the latter contact being shown on FIG. 4.

In the drawing, simplified schematic circuit patterns of relay contacts which are known in the art as symmetries have been depicted in the drawing in block diagram form. According to such patterns, the contacts are arranged to furnish one output signal if a certain combination of relays is operated at the same time. For example, H6. shows two symmetries disclosed in block diagram form. in the one symmetric associated with the relay ATK of FIG. 10, a ground signal will be applied to the winding of relay ATK through the symmetric of contacts on the five relays AT)AT4 of Fl". 10 if one and only one of the latter relays is operated. In the symmetric associated with the relays AGK and AGKA of FIG. 10, a ground signal will be applied to the windings of the latter relays if one and only one of the ten relays AGBAG9 of FIG. 18 is operated. The geometric configurations of the contacts in each of to block used in the present drawing are not shown, for they are well known in the art. For details on the construction of such configurations, reference may be made to Keister, Ritchie, and Nashburn, The Design of Switching Circuits (5th ed. 1951).

The equipment of the present invention may be advantageously incorporated in an automatic tandem telephone system wherein common control circuits are employed to control the estab. -nrnent of calls through a switching network. Gne such system is disclosed in R. B. Curtis patent application Ser. No. 31 ,275 filed concurrentl herewith. it is to be understood, however, that the present invention is not limited to use with a telephone system or" this type, but that it may also be utilized with other types of switching systems, such as local and toll systems.

The equipment illustrative of the principles of the presentinvention has been embodied in a tandem system of the type disclosed in the cited Curtis application (hereinafter referred to as the Curtis reference). it is particularly concerned with the apparatus in the dial 0 trunk circuits, the special service trunk circuits, the position link connector and position linkcontroller circuits, as well as the other circuits shown in heavy lines on FIGS. 1 and 2. The other equipment units are neither shown nor described in detail herein except where necessary for a complete understanding of the invention. Structural details of the traiiic regulator circuit are set forth in the C. E. Germanton patent application Ser. No. 318,- 427 filed concurrently herewith. The cited Curtis and Germanton applications may be consulted for a complete understanding of the construction and operation of the units not covered in detail herein.

GENERAL DESCRlPTlON The general organization of the principal equipment units of the illustrative embodiment of my invention will now be described with reference to FIGS. 1 and 2. The crossbar tandem system as disclosedin the aforementioned Curtis application is designed to serve several different classes-of-calls, such as dial 0 assistance calls and other special service calls, such as person-to-person and coin calls. Such calls are extended to the tandem system from an originating ofi'ice, such as oilice OR, via incoming trunks, such a the dial 0 and special service trunks TKtth andTK94. Each of the latter trunks is illustrative of the numerous trunks provided in a fully equipped tandem system for serving each of the diiierent classesof-calls. The trunks TKtltl and TK94 are terminated individually in the incoming trunk circuits TCGS and TC94.

Each of the latter trunk circuits has five major appearances in the switching network of the tandem system. One appearance is on the trunk link frame TLF and is used for establishing the talking connections between the calling and called stations. A second appearance is on the sender link SL and is used for passing information to and from the common control equipment, such as the sender S and marker M, of the system. Another appearance is in the call data recording equipment CDR and isused for rec rding the details required for charging for calls. A fourth appearance is in the data transfer circuit DT and is used for facilitating the interchange of data among the trunk circuits, common control. circuits, and the position control circuits, such as circuit PCC. The fifth appearance is in the operator position link connector circuit, such as circuit PLQ, and is used for connectiug the trunk circuits to operator positions on nonpriority and priority bases.

in this illustrative embodiment of my invention, the dial 0 and special service trunk circuits, such as circuits TCfhl-TC94, are segregated according to the classof-calls which they serve. There i a maximum of ten roups in each position link connector. Each such group comprises only'trunk circuits that serve the same classof-call. There are five trunk circuits in each trunk group.

This arrangement iacilitates the control over the circuit operations involved in interconnecting the trunk circuits with operator positions and permits the circuits in each class-of-service group to be served on an equitable basis.

For requesting connections to the operator positions on non-priority and priority bases, each of the dial and special service trunk circuits, such as circuits "PC00- TC%, is equipped with non-priority and priority start leads, such as the leads NPSO-NPS94 and PSO-PS94, respectively. The trunk circuits may selectively request connections to the operator positions either on a nonpriority basis or a priority basis by applying a service request signal to the appropriate non-priority or priority start lead.

It may be seen in FIG. 2 that the position link connector and the position link controller circuits, such as circuits PM and LCO, together provide the means for interconnecting the dial 0 and special service trunk circuits, such as circuits TC90TC94, with operator positions, such as positions CPI and OP66, via position control circuits and position circuits, such as the circuits FCC and PC. The position link connectors comprise the actual interconnecting means while the position link controller, as its name implies, controls the operations of a position link in such a fashion that all of the calling trunk circuits are interconnected with operator positions on an equitable basis.

The position link, such as link PLO, includes individual non-priority and priority registers, such as the registers NPRLNPRIO and PR1-PRU of FIG. 2, for each of the classof-service trunk groups for registering non-priority and priority service requests received from the associated fifty trunk circuits. Non-priority requests are received from the dial 0 and special service trunk circuits over the leads NPS-- and are applied to the non-priority registers, such as registers NPRl-NPR10, through the individual class-of-service gate circuits, such as the circuits CGl-CGIO. 'Each of these gate circuits is controlled by a traffic regulator circuit TR in order to insure that the dial 0 and special service calls received by the incoming trunk circuits are served in the approximate order in which they are presented for service.

Priority service requests from dial 0 and special service trunk circuits are received over the priority start leads PS-- and are registered in priority registers, such as the registers PR1-PR10, independently of the gating system employed for the registration of non-priority requests. As a consequence, the latter registers are eifective, as hereinafter explained, to activate a position link controller for allowing the priority requesting trunk circuits in a given trunk group to be interconnected with operator positions before any of the non-priority requesting trunk circuits in the same group.

As is indicated in FIG. 2, each position link connector in the presently disclosed embodiment has a maximum of fifty trunk circuits connected to its input and 198 position loops connected to its output. Illustrative of the latter arrangement is the connection of the trunk circuits TCllG-TC94 (fifty trunk circuits) to the input of the position link PLO and the position loops L0L197 to the output of link PLO. For connecting the trunk circuit information and control leads, such as the leads of the cables ICCO and ICC94 of FIG. 2, to the position loops, each position link employs a threestage crossbar switch network comprising a primary, secondary, and tertiary switching stage, such as the stages PR1, SEC and TER in the position link PLO of FIG. 2. The linkages connecting the primary and secondary stages PR1 and SEC are designated A links and the linkages connecting the secondary and tertiary stage SEC and TER are designated B links.

The position link connector circuit, such as circuit PLO, may be referred to for simplicity in the following description as position link PLO or as link PLO. Accordingly, this terminology is used extensively throughout the remainder of the specification. The position links are arranged together into link groups, each of which comprises ten position links. An arrangement of the position links forming one such link group and the association of those links with incoming trunk circuits, position link controllers, operator positions, a traffic regulator and other control circuits is illustrated in FIG. 2. Three link controllers are provided for each link group to control the ten position links. Preference and allotter circuits (not shown) are included in each of these link controllers to insure that equitable service is given to the incoming call traflic on each position link of a group as well as to insure that the incoming calls will be equitably distributed to the available positions.

As is illustrated in FIG. 2, a group of 66 operator positions is connected to the ten position link PLOPL9 of a link group via individual position circuits and position control circuits as well as the aforementioned 1% position loops. The latter loops are divided into 66 groups, each of which comprises three loops. A loop group, such as group LG]. comprising the loops Lil-L2, is individually associated with one of the 66 position conrol circuits, such as circuit PCC. Thus, a link group serves to interconnect any one of 500 incoming trunk circuits with any one of 66 position control circuits via 198 position loops.

Each operator is provided with a position unit, such as unit PUl of FIG. 2, which comprises a position control circuit and a position circuit. These circuits, together with the equipment at the operator position, provide three loopcircuits whereby an operator may serve calls. A position control circuit, such as circuit PCC of FIG. 2, includes facilities for automatically conditioning each of the associated loops for connecting calls one-by-one through the position circuit to the operator position. The control circuit also comprises apparatus for enabling an operator to connect her telephone to any calling loop and to place a hold condition on any calling loop while she serves a call on another loop. A key-control position control circuit, such as circuit KCP of FIG. 2 is provided for each link group and is used for selectively preconditioning the control circuits of the position units PUl- PUo for serving one of the different classes-of-calls receivable from the incoming trunk circuits.

The position control circuit PCC, the position circuit PC and the operator position 0P1 are shown to comprise three different equipment units, rather than one, only because each of the three may be physically separated from the other two by varying distances depending upon the requirements of the ofiice. However, for simplicity in discussion and ease of understanding, these three circuits may be generically referred to as the operator position circuit.

An operator can actively serve only one call at a time in this exemplary embodiment even though three loops, such as loops Lil-L2 are provided. In addition, when an operator is actively serving a call on one loop, the position link appearances of the remaining two loops will appear busy and no calls will be offered to these loops at that time. Three loop circuits are provided for each position because, on some of the calls, the calling loop may be utilized for the entire duration of the call. Ac cordingly, if only one loop circuit was provided and it was utilized for serving such a call, the operator would be idle and would have no functions to perform for the duration of the call after she had completed the services required of her in connection with the establishment of that call. By providing the three position loops, a call can be offered to any idle loop while another loop in the same group is being utilized on another call for which the operator has completed the active servicing thereof. To facilitate the serving of such a call on the idle or unused loop, the position control circuit changes the busy condition on the position link appearances of the unused loops to an idle condition after the operator com- 11 pletes the active servicing of a call. Thus, the serving of the 198 position loop circuits by 66 operator positions enables a plurality of incoming calls to be extended to and served by a plurality of operators with a minimum of waiting time between calls.

A trafiic regulator circuit, such as circuit TR of FIG. 2, regulates the equitable distribution of calls from all trunk groups in the same link group to the operator positions. The regulator controls the distribution by ascertaining the service demands by the various incoming trunk circuits as well as the availability of operator positions to serve these demands. It accomplishes the regulation by controlling the gate circuits, such as circuits CG1CG1 of FIG. 2, associated with the non-priority registers in the position link, and by controlling the position availability signals which it supplies to those position links.

The regulator comprises facilities for controlling the gate circuits to admit service requests from a group of calling trunk circuits into the non-priority registers in the position link in order that the trunk circuits may be connected on a non-priority basis to the operator positions. After the requests have been admitted and registered, the regulator closes the gates in all ten position links controlled by the regulator to lock out from those links all other trunk circuits which are in the same class-ofservice trunk groups as the circuits having already registered nonpriority requests and which may subsequently request non-priority connections to operator positions. This insures that incoming calls requesting the same class-ofservice are served in the approximate order in which they are received at the tandem ofiice. After the closure of the latter class-of-service gates, the regulator allows nonpriority service requests from trunk circuits in other class-of-service groups to be admitted and registered in the position links and these latter trunk circuits may compete for connections to the operator positions with the other trunk circuits which have previously registered non-priority service requests.

The traffic regulator also comprises circuitry which cooperates with all of the associated position links and link controllers to provide for the connection of trunk circuits to operator positions on a priority basis. When a trunk circuit requests priority service, the regulator circuitry is activated to make all operator positions appear busy to all position links which are not associated with a trunk circuit requesting priority service, while at the same time allowing the available positions to appear idle to the position link associated with the priority requesting trunk circuit. As a result, the priority requesting trunk circuit is connected through a position link to an available position before any trunk circuit requesting non-priority service, as hereinafter explained.

Non-priority request Referring to FIGS. 1 and 2, a general description is now presented of the manner in which the incoming trunk circuits are connected through a position link to available operator positions on a non-priority basis. It is presently contemplated that each calling customer will dial a directing digit or code to enable the originating office OR to determine whether dial operator assistance of special service is required on the call, and to route it to the tandem office over the appropriate one of the trunks, such as trunks TKtiti-TKM. The specific dialing routine employed for any of the calls beyonds upon a number of factorsincluding whether or not a call may be completed on a customer-dialed basis to the called station.

For simplifying the description of the non-priority service features of the presentinventiou, as well as the priority service features described in the next section, it is convenient to describe the manner in which a dial 0 call is served. This description will serve as well to explain the manner in which the other special service trunk circuits are connected to operator positions on nonpriority and priority bases since the circuit operations are essentially the same for the dial 0 and special service trunk circuits. Additionally, let it be assumed that the call data recording is to be accomplished at the tan dem ofiice and that the originating oifice OR is not equipped for automatic calling number identification (ANI). As a result, such a call will be routed to an operator at the tandem ofiice and she must orally obtain the calling station number from the caller. Such a call is referred to as a dial 0 non-ANT call in the aforementioned Curtis reference.

On a dial 0 call, this particular originating oflice OR recognizes from the dialing of the initial digit 0 that the called station digits willnot be dialed by the calling party, and it immediately establishes connections to a trunk, for example trunk TKGO, extending to the tandem office. The call is then received in the dial 0 trunk circuit TCOtl which exclusively serves calls of this type and which immediately upon its seizure requests connections to an operator position on a non-priority basis by applying a service request signal to the nonpriority start lead NPSO.

If no other dial 0 trunk circuit in the same link group as trunk circuit TCilt) has previously requested, and is yet awaiting, connections to an operator position, the dial 0 class-of-service gate circuit CGl of FIG. 2 in the position link PLG admits the non-priority request from trunk circuit T000 into the non-priority register NPRI for registration. On the other hand, if another'dial O trunk circuit in the same link group as circuit TCtlt) has previously registered a request in the register NPRl and it has not been connected to an operator position, the gate circuit CG]. will have been activated by the tralfic regulator TR of FIG. 2 to block the registration of the non-priority request from circuit TCilt) until after the previously registered request has been served.

After the service request from trunk circuit TCGO has been admitted and registered, the other control circuits of the position link PLQ are activated to send class mark data to the traflic regulator TR for informing it that a dial 0 class-of-service has been requested. This data enables regulator TR to activate the class-of-service gate circuit CGI and the other gate circuits, which corres ond to the gate circuit CGI, in all ten position link connectors of the link group. When activated, these gates temporarily block the registration of non-priority service requests from all other dial 0 trunk circuits (not shown) which may subsequently request non-priority connections to operator positions while the trunk circuit TCOO is awaiting such connections. The blocking condition then persists until after the servicing of the request from trunk circuit TC00 and all of the non-priority requests which may have been simultaneously registered in the dial 0 non-priority registers for other dial 0 trunk circuits in the same link group. This gating system insures that the calls requesting the same class-of-service are served in the approximate order in which they are presented for service.

Before explaining further details of the manner in which the dial 0 call in trunk circuit TC00 is extended to an opeartor position, it is advisable to explain that the traflic regulator TR maintains a constant check on all 66 position control circuits, such as circuit FCC, to ascertain if operator positions are available to serve the different classes-of-calls. It may be recalled that the operator positions are selectively preconditioned for serving some or all of the classes-of-calls under control of the keycontrol position control circuit KCP. This checking operation provides for the efiicient use of the associated three link controllers. The efiiciency is achieved because the regulator TR, after it has checked the availability of the positions, sends position availability signals to all ten position links and accordingly allows each such link to seize one of the three controllers only if an operator 13 is available to serve a call on a trunk circuit having a request registered to that link.

Thus, if a non-priority request from a first trunk circuit, such as a dial trunk circuit, is registered in a first position link and the call on that circuit cannot be served due to the unavailability of an appropriate operator position to serve dial 0 calls, the regulator prevents that position link from seizing an idle link controller until after an appropriate position becomes available. On the other hand, however, if a second trunk circuit request, such as a request from a special service trunk circuit, is thereafter registered in a second position link in the same link group and a position is available to serve the call on that trunk circuit but not the call on the first dial 0 trunk circuit, the regulator TR allows the second, but not the first, position link to seize an idle link controller. This mode of operation prevents the unnecessary tie-up of the link controllers by trunk circuits which cannot be served. In addition, it increases the speed of establishing connections and insures that calls are served quickly when there are operator positions available to serve them.

Returning now to the description of the manner in which the trunk circuit TCOO is connected to an operator position on a non-priority basis, it is noted that when the regulator TR informs the position link PLO that at least one position is available to serve the call on trunk circuit TCQD, the link PLO seizes an idle link controller, for example controller LCG, and transfers to it the identity of trunk circuit TC00 together with all other trunk circuits on that link which are currently requesting connections on a non-priority basis to available operator positions. Controller LCG then selects the most preferred class-of-service trunk group from among those requesting the non-priority service and then selects the most preferred calling trunk circuit, for example circuit TC00, within the selected group for connections to an available position. It should be kept in mind at this point that, in making the trunk group selection, no priority service requests are in the system at that time. Thereafter, the controller LCG informs the position link PLO that trunk circuit TCiN) is to be served. In return, that link transmits back to the controller LCO a dial 0 class-of-service indication for trunk circuit TC00 for enabling the controller LC!) to initiate the selection of an appropriate operator position to serve the call.

After selecting an available operator position, for example position OPl, controller LCO scans all possible communication channels through the primary, secondary and tertiary switching stages PR1, SEC and TER and A and B links of the position link PLO to find an idle channel capable of interconnecting trunk circuit TC00 with an idle one of the three loops to position 0P1. When an idle channel has been found, controller LCO activates the stages PR1, SEC and TER to interconnect trunk circuit TCQt) and a position loop circuit through the position control circuit PCC and position circuit PC to position 0P1. Controller LCO then releases. At the same time, the position control circuit PCC seizes the data transfer circuit D1, which then interconnects the trunk circuit TCQO with control circuit PCC in order that circuit TCtlO may transmit class mark information to circuit PCC. Shortly afterwards, the data transfer circuit releases. The established connections are thereafter held under the control of the control circuit .PCC.

Following the interconnection of trunk circuit TC00 and control circuit PCC, the operator telephone (not shown) is operatively associated with the call connections and a tone signal is sent from circuit FCC to that telephone for alerting the operator to the call. At the same time, indicator lamps (not shown) are lit at the position to notify the operator of the class-of-call to be served and the identity of the loop engaged for that call. The operator may now orally request from the calling party both the calling and called station numbers and key both of these numbers into registers (not shown at her position. She then depresses a position key (not shown) which causes the trunk circuit TCiBti to seize a sender, for example sender S, through the sender link SL. The depressed position key (not shown) also causes the data transfer circuit DT to interconnect the trunk circuit TCtlt the position of 0P1 and the sender S in order that the calling and called numbers and other information regisrered in the position control circuit PCC may be transmitted to the sender S of FIG. 1.

In response to the successful receipt of the call information in the sender S, the data transfer circuit DT is released. At the same time, sender S seizes a marker, such as marker M, via the marker connector MC, and transmits to marker M the information it needs to extend call connections from trunk circuit TCttil. Marker M selects an idle outgoing trunk circuit, for example circuit OTC, extending to the called destination and then selects and closes connections between trunk circuits TCGQ and OTC via the trunk link and ofiice link frames TLF and OLF. Once the latter connections are established, marker M releases and sender S outpulses to the next telephone ofiice the information required by that oiiice to complete the call. The sender S then releases, thereby leaving the connections within the tandem office under control of the trunk circuit TCiltl.

While the last-mentioned circuit operations are in progress, the operator may depress a key at her position to initiate the recording of the proper call charges in the call data recording equipment CDR in a manner discussed in the Curtis reference and then to release the loop circuit connecting her position to the call connections. Upon the release of this loop circuit, another call may be connected thereto in a manner as described in the foregoing paragraphs. As a result of releasing the loop circuit, that circuit is not tied up during the periods when operator assistance is not required by the customer and the operator is free to utilize these facilities to serve another call while the just-served call is in progress. In the event that the customer involved on the latter call again requires assistance, she may recall the same or another operator and be connected to the latter operators position on a priority basis.

Priority request After the call connections have been established through the trunk circuit TCGO to the called station, the calling party again may request operator assistance by momentarily depressing the telephone switchhook, or button, to send a transient on-hook signal to circuit TCOG. The latter circuit then requests connections to an operator on a priority basis by applying a signal to the priority start lead PSO of FIG. 1. This priority request signal is sent to the position link PLtl and is registered in the dial O priority register PR1 independently of the gating system used for the previously described nonpriority service. After the priority request has been registered, the other control circuits of the position link PLO activate the trafiic regulator TR which then makes all operator positions appear busy to the position links in the same link group that are not engaged in serving priority requests. Consequently, none of the latter position links can seize a position link controller for serving a non-priority request until after all of the priority requesting trunk circuits have been connected to operator positions. In addition, the trailic regulator TR activates the control gates for the non-priority registers associated with the dial 0 trunk circuits on all position links Pill-P19 to block the subsequent registration of non-priority requests from these registers until after the priority requesting trunk circuit TCGG has been interconnected with an operator position.

When there is a position available to serve a priority request, the regulator TR enables a preferred one of the position links having a registered priority request to seize 

